The present invention relates generally to engine air intake assemblies, and more particularly, to an idle air bypass tube for use with engine air intake assemblies.
In general, internal combustion engines include at least one cylinder constructed to receive combustion gases that pass through an air intake opening formed in a throttle body attached to the engine. Typically, the amount of combustion gas provided to the cylinder is partly controlled by the position of a throttle plate. As an operator desires increased output from the engine, the operator advances a throttle actuator which in turn opens the throttle plate thereby providing increased amounts of combustion gas to the cylinders. In addition to mechanically actuating the throttle plate, the throttle actuator also initiates increased fuel supplied to the cylinders. In fuel injected engines, the throttle actuator signals an ECU to increase an amount of fuel supplied to the cylinders by a fuel system and, in carbureted engines, the throttle actuator mechanically provides more fuel to the cylinders. As an operator increases the engine speed from idle, the throttle plate gradually opens an amount that is generally proportional to the operator initiated change in throttle actuator position thereby providing more combustion gas to the cylinders of the engine.
As the throttle plate opens in response to the throttle command, in addition to allowing more combustion gas, or air, to pass into the engine, increased amounts of engine noise are allowed to exit the engine through the throttle body and past the throttle plate. Additionally, some known throttle plates have holes formed therethrough. These holes provide an appropriate amount of combustion gas necessary for idle operation of the engine. Those throttle plates which have holes formed therethrough, may cause a whistling, or chirping sound. Alternatively, the throttle plate is held open to allow sufficient air to pass by to maintain idle speed. Those that are held open generally allow engine noise to pass unobstructed. Combustion noise allowed to exit the engine via the air intake, in addition to any whistling or chirping caused by the throttle plate idle holes, can be a distraction to an otherwise well-performing engine. Additionally, a quieter operating engine that eliminates any noise is generally advantageous.
Previous attempts have been made to reduce the amount of engine noise emitted from the air intake assembly of an engine. Some of these attempts include subjecting the flow of incoming air to a tortuous path through a muffling material positioned over the intake opening of the air intake assembly. Other approaches involve placing a muffling material within a recess formed in a housing positioned about the engine. Air for engine combustion is only allowed to enter the housing by passing through the muffling material. Both of these approaches significantly reduce the movement of air to the air intake assembly, periodically require servicing, such as cleaning or replacement of the muffling material, and add excess cost. Additionally, the muffling materials, as they absorb particulate matter, provide the engine with a variable flow of combustion gas to the engine. This variable flow of combustion gas makes precision engine combustion calibration difficult to initially set and even more difficult to maintain.
It would therefore be desirable to have an engine with a throttle assembly that reduces the amount of noise emitted from the main air intake. To this end, it would be desirable to operate the engine with the throttle plate in a closed position for a range of throttle actuator inputs while providing an unrestricted flow of combustion gas through the throttle assembly and to the engine.